As you learned earlier, the domain is the basic unit of organization in Active Directory. Here, you can see the root domain within the larger
context of Active Directory:
When you install Active Directory for the first time in a network, you create the first domain controller in the forest, thus establishing the root domain 
The root domain contains the configuration and schema information for the forest.
To create a root domain, run the
file to start the Active Directory Installation Wizard.
Once the wizard is launched, you will complete a series of steps to create a root domain. The following simulation guides you through this process:
After you finish specifying the installation information, the Active Directory Installation Wizard installs Active Directory, converts the computer to a domain controller, and adds the following three consoles
to the Administrative Tools menu on that computer.
These consoles will be installed with the completion of all the installation paths.
Microsoft Management Console (MMC):
A framework for hosting administrative tools, called consoles. A console may contain tools, folders or other containers, World Wide Web pages, and other administrative items. These items are displayed in the left pane of the console, called a console tree.
Here is what the Administrative Tools menu should look like once you have added the consoles:
As you pursue other installation options (such as establishing a child domain or a tree), you will find that the process for installing various parts of Active Directory with the wizard are remarkably similar to the one described above.
The lessons that follow will remind you of this process and will point out what is different about them. But if you find yourself wanting a review of what the wizard will do at each and every step, return to this lesson. In this lesson, you created a root domain and a domain controller for that root domain. You will build on that skill in the next lesson by creating a domain controller in an already existing domain.
Click the Exercise link below to try creating a root domain on your own.Create Root Domain